[Station X]

Sounds like we're back to square one. Best to check whether T1 secondary is faulty.

Remove TR6 and TR7.
Meter on 200 ohm range.
One lead of meter connected to junction of R26 and R27.
Other meter lead connected to point to which TR6 base was connected. Note reading.
Other meter lead connected to point to which TR7 base was connected. Note reading.
If you get an over range indication switch to the 2000 ohm range.
Report readings here.
Both halves of the winding should show continuity.

Meter on 2000mV (2 volt) range.
Red lead of meter connected to chassis
Turn on the set.
Black meter lead connected to point to which TR6 base was connected. Note reading.
Black meter lead connected to point to which TR7 base was connected. Note reading.
If necessary switch up or down a range for a more accurate reading.
Report readings here.
You should see about 0.2V (200mV) on each base track.